Method of generating energy in a power plant comprising a gas turbine, and power plant for carrying out the method

Abstract

A method of generating energy in a power plant ( 30 ) having a gas turbine ( 29 ), includes a first step a gas containing air ( 1 ) is compressed in a first compressor ( 2 ) of the gas turbine ( 29 ), a second step the compressed gas ( 3, 3 a, 3 b; 5; 7 a, 7 b ) is fed to a combustion process with the addition of fuel ( 8 ) in a combustor ( 23 ), a third step the hot flue gas ( 9 ) from the combustor ( 23 ) is expanded in an expander or a turbine ( 10 ), driving a generator ( 18 ), of the gas turbine ( 29 ) while performing work, and a fourth step a partial flow of the expanded flue gas ( 11 ) is recirculated to the inlet of the first compressor ( 2 ) and admixed with the gas containing air ( 1 ). Carbon dioxide (CO 2 ) is separated from the compressed gas ( 3, 3 a, 3 b; 5; 7 a, 7 b ) in a CO 2 separator ( 6 ) before the third step. In such a method, the overall size and energy costs are reduced by virtue of the fact that, to permit increased CO 2 concentrations in the CO 2 separator ( 6 ), not more than about 70 % of the carbon dioxide contained in the compressed gas ( 3, 3 a, 3 b; 5, 5 a, 5 b; 7 a, 7 b ) is removed from the compressed gas ( 3, 3 a, 3 b; 5, 5 a, 5 b; 7 a, 7 b ).

1 . A method of generating energy in a power plant including a gas turbine, the method comprising: 
 first compressing a gas containing air in a first compressor of the gas turbine;    second feeding the compressed gas to a combustion process with fuel in a combustor to generate hot flue gas;    third expanding the hot flue gas from the combustor in an expander or a turbine, and driving a generator, of the gas turbine while performing work; and    fourth recirculating at least a partial flow of the expanded flue gas to an inlet of the first compressor and admixing with the gas containing air, and separating carbon dioxide (CO 2 ) from the compressed gas in a CO 2  separator before said expanding;    wherein separating comprises removing from the compressed gas not more than about 70% of the carbon dioxide contained in the compressed gas to permit increased CO 2  concentrations in the CO 2  separator.    
     
     
         2 . The method as claimed in  claim 1 , wherein recirculating comprises recirculating the entire flow of the compressed gas through the CO 2  separator, and wherein removing comprises removing between 10% and 70% of the carbon dioxide contained in the compressed gas.  
     
     
         3 . The method as claimed in  claim 1 , comprising: 
 splitting up the entire flow of the compressed gas into a larger partial flow and a smaller partial flow, and passing only the smaller partial flow through the CO 2  separator and removing from the compressed gas more than 50% of the carbon dioxide contained in the compressed gas.    
     
     
         4 . The method as claimed in  claim 1 , comprising: 
 cooling down the compressed gas in a heat exchanger before entering the CO 2  separator.    
     
     
         5 . The method as claimed in  claim 1 , comprising: 
 cooling down the flue gas expanded in the turbine in a heat exchanger, or using the flue gas expanded in the turbine in a heat-recovery steam generator for generating steam.    
     
     
         6 . The method as claimed in  claim 1 , comprising: 
 extracting water in a condenser from the at least partial flow of the flue gas before mixing with the gas containing air.    
     
     
         7 . The method as claimed in  claim 2 , comprising: 
 passing the compressed gas from the CO 2  separator directly to the combustor.    
     
     
         8 . The method as claimed in  claim 2 , comprising: 
 extracting heat with the compressed gas coming from the CO 2  separator first in a gas/gas heat exchanger from the compressed gas from the first compressor, and after said extracting heat passing said compressed gas to the combustor.    
     
     
         9 . The method as claimed in  claim 2 , comprising: 
 compressing the compressed gas coming from the CO 2  separator further in a second compressor of the gas turbine; and    feeding the further compressed gas to the combustor.    
     
     
         10 . The method as claimed in  claim 3 , comprising: 
 passing the compressed gas coming from the CO 2  separator directly to the combustor.    
     
     
         11 . The method as claimed in  claim 3 , comprising: extracting heat with the compressed gas coming from the CO 2  separator first in a gas/gas heat exchanger from the compressed gas coming from the first compressor, and after said extracting heat passing said compressed gas to the combustor.  
     
     
         12 . The method as claimed in  claim 3 , comprising: 
 cooling a hot-gas duct of the turbine with the compressed gas coming from the CO 2  separator.    
     
     
         13 . The method as claimed in  claim 3 , comprising: 
 compressing the compressed gas coming from the CO 2  separator further in a second compressor of the gas turbine; and    feeding the further compressed gas to the combustor.    
     
     
         14 . The method as claimed in  claim 1 , comprising: 
 further compressing the compressed gas coming from the CO 2  separator in a second compressor; and    optionally adding oxygen to the further compressed gas.    
     
     
         15 . The method as claimed in  claim 1 , wherein said air comprises air enriched with oxygen.  
     
     
         16 . The method as claimed in  claim 1 , comprising: 
 preheating compressed gas coming from the CO 2  separator in a gas/gas heat exchanger before entering the combustor, with hot flue gas issuing from the turbine.    
     
     
         17 . The method as claimed in  claim 1 , comprising: 
 generating steam with hot flue gas issuing from the turbine; and    injecting a portion of the generated steam into the combustor, and using a portion of the generated steam in the CO 2  separator.    
     
     
         18 . The method as claimed in  claim 17 , comprising: 
 compressing the compressed gas coming from the CO 2  separator subsequently in a booster compressor; and    exchanging heat between the subsequently compressed gas and the compressed gas coming from the first compressor, in a gas/gas heat exchanger.    
     
     
         19 . The method as claimed in  claim 1 , comprising: 
 humidifying compressed gas coming from the CO 2  separator in a humidification device before entering the combustor; and    extracting heat with the humidified gas, before entering the combustor, in a gas/gas heat exchanger from compressed gas issuing from the first compressor.    
     
     
         20 . A power plant useful for carrying out the method as claimed in  claim 1 , comprising: 
 a gas turbine having 
 a first compressor with an inlet and outlet,  
 a combustor having a first inlet for compressed gas, a second inlet for fuel, and an outlet for hot flue gas,  
 a condenser having an inlet and an outlet, and  
 a turbine with an inlet and outlet, the outlet of the combustor being connected to the inlet of the turbine, the outlet of the turbine being connected via the condenser to the inlet of the first compressor, and the outlet of the first compressor being connected to the first inlet of the combustor;  
   a heat exchanger; and    a CO 2  separator having an inlet side connected to the outlet of the first compressor via the heat exchanger, and having an outlet side connected to the first inlet of the combustor;    wherein the CO 2  separator is configured and arranged to separate not more than 70% of the carbon dioxide of the compressed gas coming from the first compressor.    
     
     
         21 . The power plant as claimed in  claim 20 , further comprising: 
 a single connecting line leading from the outlet of the first compressor to the first inlet of the combustor;    wherein the CO 2  separator is positioned in said single connecting line; and    wherein the CO 2  separator is configured and arranged so that the CO 2  separator separates not more than 70% of the carbon dioxide of the gas flowing therethrough.    
     
     
         22 . The power plant as claimed in  claim 20 , further comprising: 
 two connecting lines leading from the outlet of the first compressor in parallel to the first inlet of the combustor; and    wherein the CO 2  separator is positioned in one of said two connecting lines.    
     
     
         23 . The power plant as claimed in  claim 20 , wherein said heat exchanger comprises a first heat exchanger, and further comprising: 
 a second heat exchanger or a heat-recovery steam generator arranged between the outlet of the turbine and the inlet of the condenser.    
     
     
         24 . The power plant as claimed in  claim 20 , further comprising: 
 a second compressor arranged between the outlet of the CO 2  separator and the first inlet of the combustor.    
     
     
         25 . The power plant as claimed in  claim 20 , further comprising: 
 a gas/gas heat exchanger connected to the outlet of the turbine and arranged between the outlet of the CO 2  separator and the first inlet of the combustor.    
     
     
         26 . The power plant as claimed in  claim 20 , further comprising: 
 a device for generating steam arranged at the outlet of the turbine and connected to the combustor and to the CO 2  separator; and    a booster compressor and a following gas/gas heat exchanger arranged between the outlet of the CO 2  separator and the first inlet of the combustor.    
     
     
         27 . The power plant as claimed in  claim 20 , further comprising: 
 a humidification device arranged between the outlet of the CO 2  separator and the first inlet of the combustor.    
     
     
         28 . The method as claimed in  claim 3 , wherein removing comprises removing from the compressed gas between 70% and 99% of the carbon dioxide contained in the compressed gas.